There is a known detecting device detecting the rotational position of a magnetic moving body using a magnet and a magnetoelectric conversion element. The magnetoelectric conversion element referred herein means an element having a resistance value that changes in accordance with the applied magnetic field, such as an MR (Magneto-Resistance) element, a GMR (Giant Magneto-Resistance) element, and a TMR (Tunnel Magneto-Resistance) element.
For example, the magnetic position detecting device disclosed in Japanese Patent Laying-Open No. 2004-109113 (PTL 1) includes a processing circuit unit and a magnet. The processing circuit unit is disposed above and spaced apart from a plane of a magnetic moving body rotating in the circumferential direction and having a peripheral edge portion that is provided with a plurality of radially protruding protrusions. The processing circuit unit has a bridge circuit including the first magnetoresistance segment and the second magnetoresistance segment. The magnet applies a magnetic field to the first and second magnetoresistance segments, and also applies a magnetic field to the magnetic moving body in the direction of the rotation axis line of the magnetic moving body. The second magnetoresistance segment is disposed approximately on the center line in the width dimension in the circumferential direction of the magnet as seen in the direction of the rotation axis line. The first magnetoresistance segment is disposed on the side to which the magnetic moving body is displaced with respect to the second magnetoelectric conversion element. The processing circuit unit obtains a differential output from the outputs of the first magnetoresistance segment and the second magnetoresistance segment.
In the magnetic position detecting device disclosed in the above-mentioned literature, a flux guide made of a magnetic material is further provided between the processing circuit unit and the magnet. The flux guide has a pair of protrusions facing each other and spaced apart from each other in the circumferential direction of the magnetic moving body. The second magnetoelectric conversion element is disposed approximately on the central line between the pair of protrusions. The first magnetoelectric conversion element is disposed on the side of one of the protrusions.